Swept frequency acoustic interferometry (SFAI) [1] is an adaptation of the techniques of ultrasonic interferometry developed several decades ago for determining sound velocity and absorption in liquids and gases. In the original technique, and also in more recent modifications of the technique [2], the transducers (sensors) were placed in direct contact with the fluid being tested. This restricted the use of this technique to highly specialized laboratory characterization of fluids. By contrast, the SFAI technique extends the capabilities of the ultrasonic interferometry technique significantly and allows the noninvasive determination of velocity and attenuation of sound in a fluid (liquid, gas, mixtures, emulsions, etc.,) inside sealed containers (pipes, tanks, chemical reactors, etc.) over a wide frequency range. In addition, if the container material properties (density and sound velocity) are known, the liquid density can be determined using the SFAI technique. It has also been shown that it is possible to uniquely identify various chemical compounds and their most significant precursors based on the physical parameters of sound: velocity, attenuation, frequency dependence of sound attenuation, and density [3].
Oil companies have recently shown interest in noninvasive techniques for characterizing oil flow in pipes from oil fields.
U.S. Pat. No. 5,606,130 [4] states that it is anticipated that the SFAI measurements described therein can be performed on flowing samples in pipes. However, no mention is made therein of how to perform such measurements.
Accordingly, it is an object of the present invention to provide an apparatus and method for determining the composition of flowing fluids.
Another object of the invention is to provide an apparatus and method for determining the flow rate of a fluid.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.